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Natl. Acad. Sci. U.S.A."],"published-print":{"date-parts":[[2026,6,2]]},"abstract":"<jats:p>Convection in porous materials governs heat transport across scales ranging from planetary subsurface systems to engineered cooling devices. While the onset of buoyancy-driven flow is well described by linear stability theory within a porous-continuum representation, the subsequent transition from viscous, matrix-dominated convection toward inertia-influenced and ultimately bulk fluid-like plume convection has lacked a unified description. Here we develop a confinement-based scaling framework that connects these flow states through a common scale-ratio perspective and quantitatively bridges classical porous convection with laterally confined Rayleigh\u2013B\u00e9nard systems. Because random porous and fractured media do not admit an obvious static scale-ratio, we recover an effective confinement measure from the onset condition. This links permeability-based systems to the classical confinement framework and defines a characteristic pore length for natural convection. Comparing this pore length with the thermal boundary-layer thickness yields a dynamic criterion for the emergence of unconfined behavior. Embedding experimental and numerical porous\u2013convection datasets into a unified phase diagram of buoyant forcing and static confinement reveals a systematic progression from viscous, drag-dominated heat transport to inertia-corrected flow and ultimately to plume-driven convection whose statistics approach those of unconfined fluids. The resulting framework delineates the limits of porous-continuum validity, clarifies when inertial corrections become relevant, and highlights the dynamical analogy between strongly confined porous flows and thin-gap Hele\u2013Shaw configurations. By linking heat-transport scaling to static and dynamic length scales, the phase diagram provides a practical diagnostic for selecting appropriate governing equations across geophysical and engineered porous systems.<\/jats:p>","DOI":"10.1073\/pnas.2533675123","type":"journal-article","created":{"date-parts":[[2026,5,28]],"date-time":"2026-05-28T18:07:28Z","timestamp":1779991648000},"update-policy":"https:\/\/doi.org\/10.1073\/pnas.cm10313","source":"Crossref","is-referenced-by-count":3,"title":["Dynamic confinement controls the porous-to-free convection transition"],"prefix":"10.1073","volume":"123","author":[{"ORCID":"https:\/\/orcid.org\/0009-0006-1984-992X","authenticated-orcid":false,"given":"Dario M.","family":"Schwendener","sequence":"first","affiliation":[{"id":[{"id":"https:\/\/ror.org\/05a28rw58","id-type":"ROR","asserted-by":"publisher"}],"name":"Department of Earth and Planetary Sciences","place":["Zurich, Switzerland"]},{"name":"Institute of Geophysics, Geothermal Energy and Geofluids Group","place":["Zurich, Switzerland"]},{"name":"ETH Z\u00fcrich","place":["Zurich, Switzerland"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Jerome","family":"Noir","sequence":"additional","affiliation":[{"id":[{"id":"https:\/\/ror.org\/05a28rw58","id-type":"ROR","asserted-by":"publisher"}],"name":"Department of Earth and Planetary Sciences","place":["Zurich, Switzerland"]},{"name":"Institute of Geophysics","place":["Zurich, Switzerland"]},{"name":"Earth and Planetary Magnetism, Institute of Geophysics","place":["Zurich, Switzerland"]},{"name":"ETH Z\u00fcrich","place":["Zurich, Switzerland"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Jonas","family":"Latt","sequence":"additional","affiliation":[{"id":[{"id":"https:\/\/ror.org\/01swzsf04","id-type":"ROR","asserted-by":"publisher"}],"name":"Department of Computer Science","place":["Carouge, Switzerland"]},{"name":"University of Geneva","place":["Carouge, Switzerland"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-0711-9819","authenticated-orcid":false,"given":"Christophe","family":"Coreixas","sequence":"additional","affiliation":[{"id":[{"id":"https:\/\/ror.org\/01swzsf04","id-type":"ROR","asserted-by":"publisher"}],"name":"Department of Computer Science","place":["Carouge, Switzerland"]},{"name":"University of Geneva","place":["Carouge, Switzerland"]},{"id":[{"id":"https:\/\/ror.org\/04snvc712","id-type":"ROR","asserted-by":"publisher"}],"name":"Institute for Advanced Study","place":["Zhuhai, China"]},{"name":"Beijing Normal\u2013Hong Kong Baptist University","place":["Zhuhai, China"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-6254-2428","authenticated-orcid":false,"given":"Xiang-Zhao","family":"Kong","sequence":"additional","affiliation":[{"id":[{"id":"https:\/\/ror.org\/05a28rw58","id-type":"ROR","asserted-by":"publisher"}],"name":"Department of Earth and Planetary Sciences","place":["Zurich, Switzerland"]},{"name":"Institute of Geophysics, Geothermal Energy and Geofluids Group","place":["Zurich, Switzerland"]},{"name":"ETH Z\u00fcrich","place":["Zurich, Switzerland"]}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"341","published-online":{"date-parts":[[2026,5,28]]},"reference":[{"key":"e_1_3_4_1_2","doi-asserted-by":"publisher","DOI":"10.1038\/ncomms8837"},{"key":"e_1_3_4_2_2","doi-asserted-by":"publisher","DOI":"10.1038\/s41550-017-0289-8"},{"key":"e_1_3_4_3_2","doi-asserted-by":"publisher","DOI":"10.1002\/htj.22377"},{"key":"e_1_3_4_4_2","doi-asserted-by":"publisher","DOI":"10.1007\/s10040-010-0657-2"},{"key":"e_1_3_4_5_2","doi-asserted-by":"publisher","DOI":"10.1017\/jfm.2020.309"},{"key":"e_1_3_4_6_2","doi-asserted-by":"publisher","DOI":"10.1103\/PhysRevA.42.3650"},{"key":"e_1_3_4_7_2","doi-asserted-by":"publisher","DOI":"10.1017\/S0022112099007545"},{"key":"e_1_3_4_8_2","doi-asserted-by":"publisher","DOI":"10.1017\/jfm.2016.578"},{"key":"e_1_3_4_9_2","doi-asserted-by":"publisher","DOI":"10.1029\/2010GL044728"},{"key":"e_1_3_4_10_2","doi-asserted-by":"publisher","DOI":"10.1017\/jfm.2023.246"},{"key":"e_1_3_4_11_2","doi-asserted-by":"publisher","DOI":"10.1103\/PhysRevLett.108.224503"},{"key":"e_1_3_4_12_2","doi-asserted-by":"publisher","DOI":"10.1017\/jfm.2022.491"},{"key":"e_1_3_4_13_2","volume-title":"The Method of Volume Averaging","author":"Whitaker S.","year":"2013","unstructured":"S. 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